Multnomah County prosecutors won’t pursue criminal charges against a driver who was accused of intentionally swerving into a downtown Portland bicyclist after an argument over her driving skills.

Deputy District Attorney Chris Ramras wrote in a decline-to-prosecute memo that he didn’t think his office could prove beyond a reasonable doubt that Celine Julia Geday struck cyclist Brian Lee Groce on purpose. Groce was injured badly enough for Geday to be arrested on accusations of second-degree assault.

According to Ramras’ memo:

The incident unfolded about noon on April 3 after Geday, a philosophy student at Portland State University, left class, got into her car and began to pull out from the curb on Southwest Jackson Street. Groce, 47, thought Geday nearly hit him and he yelled at her. Geday, 29, honked her horn in response and drove off.

Celine GedayMultnomah Co. Sheriff's Office

But Groce caught up with her about a block later, near Southwest Broadway. He rode up next to her driver’s side window. That’s when his bike and Geday’s sideview mirror made contact, and Groce injured his face as he fell to the pavement.

Geday denied that she intentionally hurt Groce, even though police told her -- incorrectly, the prosecutor noted -- that three witnesses had seen her intentionally strike him.

After Geday’s arrest, detectives got a chance to interview the witnesses in detail. And the prosecutor concluded that only one of the three saw the impact. That witness said she thought Geday swerved to the left, causing the impact -- but the witness couldn’t describe “any real change in the angle” of Geday’s 2003 Volkswagen Jetta.

“This leads one to conclude that if Ms. Geday swerved to the left, it was very minimal in nature,” Ramras wrote.

Ramras also wrote that because Geday might have been focusing on Groce as he approached on his bicycle -- and Groce might have been leaning in to talk or shout at her -- the two likely moved slightly toward each other without intending to cause a crash.

“In this case, Mr. Groce placed himself into a very dangerous situation by illegally leaving his proper lane of travel to ride alongside the driver’s side door in order to continue to verbally engage with Ms. Geday after she had already left the scene of their initial encounter,” Ramras wrote. “There is no question he was still upset by their initial encounter and in fact he agrees that he was angry and that he made a mistake in trying to catch up to her.”

If the case had gone to trial, the prosecutor wrote, Geday’s defense could argue that Groce has a “reputation for being violent.” Ramras said Groce was convicted in 2008 of attempted second-degree assault for stabbing his then-domestic partner while his partner tried to hold up a bicycle to protect himself.

In 2010, Groce was arrested on an accusation of disorderly conduct for allegedly becoming “aggressive and threatening towards police when he was arrested while walking intoxicated on a street,” Ramras wrote. Groce was allowed to avoid a conviction after completing a diversion program.

On the flip side, Geday doesn’t have a spotless history, either. Ramras wrote that she was arrested in Washington under allegations of assaulting her mother. But “it appears that this was also dealt with in some sort of early resolution manner as she does not have a conviction for this incident.”

Ramras concluded his memo by saying there also was insufficient evidence to prove that Geday “recklessly” caused the crash -- and so his office wouldn’t pursue lesser charges of fourth-degree assault, recklessly endangering another or reckless driving.

The memo does not address an issue Groce brought up. The day after the encounter, Groce told The Oregonian that it started after he saw Geday apparently texting, she cut him off and he yelled she was an "idiot." He said he might have inserted an expletive in front of "idiot."

Groce said Geday flipped him off and honked her horn. The DA's memo doesn't reference anything about Geday's alleged hand gesture or texting.